Custom orderby in Product Sorting only uses first digit

I’ve added a custom filter to the product sorting select dropdown, and it works – but it only uses the first digit of the number when sorting the results.

For example, lowest to highest would get listed like:

1, 2, 22, 25, 3, 39, 4, 5, 56, 6….

when it should be:

1, 2, 3, 4, 5, 6, 22, 25, 39, 56…

anyone know how to fix this?

Thanks!

https://www.ads-software.com/plugins/woocommerce-product-sort-and-display/